Escalation occurs only if the balance of resolve is uncertain. If each state believes that it is likely to be more resolute than its adversary, then each may escalate in the expectation that the other will back down. As the crisis continues and neither state backs down, each learns that the other is more resolute than initially believed. Eventually one state concludes that the risk is too high and the chances that the other will back down are too low to warrant further escalation. At that point that state backs down and the crisis ends – assuming, of course, that events have not already gone out of control.

Brinkmanship can be seen as a variant of an all-pay, second-price auction in which bids are measured in terms of the risk that events will go out of control. The political conflict of interest underlying the crisis defines the payoffs to winning or losing the auction. In order to win, each state bids up the risk until one of the states finds the risk too high and quits. The state that prevails is the one that is willing to hang on longer, that is, makes the highest bid. But the amount of risk that the states actually run during the crisis is determined by the state that backs down first. Thus, the “price” that each state must pay – that is, the risk of disaster each must run – is determined not by the highest bid but by the second-highest bid.

In sum, according to nuclear deterrence theory, nuclear weapons change the strategic setting in which political conflicts play out by transforming crises from contests of relative military strength into contests of resolve. We can then explain the dynamics of the latter in terms of the logic of brinkmanship. States exert coercive pressure on each other during a crisis by taking steps that raise the risk that the crisis will go out of control. States make “threats that leave something to chance,” as Schelling called them.

Is Nuclear Deterrence Theory A Cold-War Relic?

Before trying to think through the consequences of nuclear proliferation, it is important to distinguish between two questions. First, does nuclear deterrence theory still provide a useful guide to the logic of escalation and the way that crises between nuclear states play out? If the answer to this question is “no,” then we have to go back to the blackboard to see if we can develop a new post-Cold War theory of nuclear crises and escalation. If the answer is “yes,” then we can use the theory to help answer a second question. Can the United States successfully deter adversaries from challenging US interests? In other words, does deterrence work from Washington’s perspective?

Not surprisingly, policymakers and analysts in Washington tend to focus on the second question. But then they often mistakenly treat a negative answer to the second as a negative answer to the first. That is, if the spread of nuclear weapons means that Washington is less likely to get its way in future crises, then there must be something wrong with our thinking about the way crises work. Clearly this is not so. The balance of resolve will not always favor the United States, and deterrence will always seem to fail from the losing side’s perspective.

When the Bush Administration took office in 2001, many both inside and outside the government seemed to believe that nuclear deterrence theory was at best an irrelevant artifact of Cold War thinking and at worst dangerously misleading. Indeed, this was a major argument in favor of developing a national missile defense system. The United States, according to those critics, could no longer rely on deterring potential adversaries. As Secretary of Defense Donald Rumsfeld argued shortly after taking office during testimony to the Senate Armed Services Committee in 2001, failing to build a missile defense system “could give rogue states the power to hold our people hostage to nuclear blackmail – in an effort to prevent us from projecting force to stop aggression.”

Rather than demonstrate that deterrence theory is irrelevant or dangerously misleading, Secretary Rumsfeld’s comments, along with those of many other observers, suggest that we can use deterrence theory to think through the consequences of nuclear proliferation. The essence of Rumsfeld’s concern is that the spread of nuclear weapons (in the absence of an effective missile defense) will likely lead to situations in which a nuclear-armed adversary would be able to deter the United States from projecting its conventional military power in ways that it otherwise would not. Secretary of Defense Robert Gates echoed this reasoning during his confirmation hearings when he expressed his concerns about the effects of North Korea and Iran’s nuclear programs; “one of the reasons why Iran is determined to have nuclear weapons is that they see how complicated it is for us to try and deal with a North Korea that has nuclear weapons.” That is, the United States may fail to deter an opponent just as deterrence theory predicts, precisely because the balance of resolve may often favor the adversary. In brief, nuclear deterrence theory remains a useful conceptual framework and analytic tool after the Cold War.

Some Implications

What does nuclear deterrence theory say about the consequences of nuclear proliferation? We highlight three implications here. First, it is clear why a militarily weak state facing a much stronger adversary has an incentive to acquire nuclear weapons. A weak state is at a severe disadvantage in any confrontation with a much stronger adversary as long as the ultima ratio is a test of conventional forces. By transforming the confrontation into a contest of resolve, nuclear weapons shift the advantage to the state with the greatest resolve which will often be the conventionally weak state. Indeed, this is especially likely to be the case if the stronger threatens the weaker with regime change. Most regimes are willing to run greater risks to stay in power than others are willing to run in order to topple them.

A second implication follows immediately. Insofar as the United States will be the overwhelming conventional power in any dispute for many years into the future, the spread of nuclear weapons will, at least to some degree, reduce the United States’ ability to use its military power to influence events.